1. Field of the Invention
The present invention relates to a human machine interface (HMI) device and an interface integration method thereof. More particularly, the HMI device and the interface integration method thereof of the present invention use an interface-oriented mechanism to establish a correspondence relation with a programmable logic controller (PLC).
2. Descriptions of the Related Art
A typical automatic control system mainly comprises two blocks: a programmable logic controller (PLC) and a human machine interface (HMI) device. Specifically, the PLC is mainly responsible for the execution of logic programs, including logic operations, operations of a counter and a timer, data input and output (I/O) and the like. A logic program may be a set of program codes, a function or a modularized functional block. Generally, various variants of logic programs are collectively termed as program units. On the other hand, the HMI device is mainly responsible for planning of an operation screen, and can be used to arrange buttons, images, charts, sampling and alarming components and the like in the screen so that a user can operate and design the system via the HMI device.
In practice, the HMI device focuses on operational convenience for the user, so it must provide a user-friendly interface for the user to compose and design the frames; on the other hand, the PLC mainly focuses on the programming and execution of logic programs. Accordingly, most automatic control system suppliers design a compiler specific to the HMI device and a compiler specific to the PLC separately. Because of the different compilers, the program units of the PLC and the interface of the HMI device must be designed separately.
In a conventional automatic control system, the PLC and the HMI device communicate with each other mainly through common variables defined therebetween and via a physical connection such as a serial port, an Ethernet or a wireless bus according to a user-defined communication protocol.
However, the complexity in interaction between the HMI device and the program units of the PLC increases correspondingly when the number of program units increases with the enlargement of the automatic control system architecture. Thus, the common variables are necessary to be defined with more complexity, which further add the burden to the user. Moreover, since there is not an adjustable flexibility in correspondence to the variables between the conventional HMI device and the program units of the PLC, it is difficult to modify corresponding variables of the HMI device when different program units are added or modified.
In view of this, efforts still have to be made in the art to overcome the shortcoming of the conventional HMI device; that is, in the prior art, it is difficult to modify variables of the HMI device because of a complicated correlation between the variables of the HMI device and the program units of the PLC.